"They have done a lot of work to search for survivors but they couldn't search all the places in such a large area here and there may be some places that they ignored."
The Chinese government has appealed for basic equipment to help in the rescue operation.
It said hammers, cranes, shovels and rubber boats were urgently needed.
The health ministry says there will also be an increasing demand for medicines and sophisticated medical equipment as survivors are treated for bone fractures, crushed internal organs and kidney failure.
More than 10,000 medical workers, police and volunteers have been sent to Beichuan County, one of the hardest-hit areas in Sichuan province, where up to 5,000 are thought to have died.
But there were suggestions that some of those trying to help bring relief were actually hindering the rescue effort, blocking roads to the worst-hit areas.
"Passionate but inexperienced volunteers have brought little food and their vehicles are blocking roads," the Chengdu chapter of the Young Communist League said in a statement read out on local TV.
RECENT CHINA QUAKES
March, 2008: 7.2 quake in Xinjiang - damage limited
February 2003: 6.8 quake in Xinjiang - at least 94 dead, 200 hurt
January 1998: 6.2 quake in rural Hebei - at least 47 dead, 2,000 hurt
Meanwhile 17 people were disciplined for allegedly spreading "malicious rumours" about the earthquake, two of whom were put in custody, AFP news agency quoted state media as saying.
Deputy Health Minister Gao Qiang says more than 64,040 people have been treated since Monday's earthquake - 12,587 of them are seriously injured, Xinhua reports.
Officials say about 10 million people have been affected by the quake. Many are in refugee camps, without proper shelter, food or clean water.
The International Federation of Red Cross and Red Crescent Societies has issued an emergency appeal for medical help, food, water and tents.
Gu Qinghui, a member of the Red Cross assessment team told AP television: "I just came back from Beichuan County this morning, basically the whole county has been destroyed, there is no Beichuan County anymore.
"No-one knows what has happened in particular areas, in the villages. I am sure that the numbers [death toll] will just go up continuing day by day."
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